Abstract: An improved data compression system and method is disclosed. The data compression method uses smaller fixed bit words to represent streams of digital data. The fixed bit words are sent instead of the streams of digital data. A table relating the fixed bit words and streams of digital data is provided as a dictionary. Each entry has a node which is indexed in a stored index. As additional fixed bit words are established for new streams of digital data, older fixed bit words are deleted from the dictionary. The older fixed bit words are prevented from being deleted if they are used for subsequent streams of data. There are a number of methods to determine how the older fixed bit words are retained which are disclosed.

Abstract: A method and apparatus for processing convolution coded data. The method and apparatus have lower computational requirements, while still reducing or eliminating errors caused by noise or distortion. A path metric value associated with each decoder state is updated upon the receipt of each incoming signal value. The path metric value is formed by: (1) identifying those permissible transition(s) to that decoder state that are represented by symbols having the minimum branch metric compared to the received signal value; (2) identifying those permissible transition(s) to that decoder state that originate from states with the minimum previously-computed path metric value; and (3) comparing the transitions identified in the first and second steps. From this comparison, the identity of the transition with the lowest path metric value is derived. Thereafter, the path metric chosen is stored for that given state.